Method adn apparatus for turf aerifcation

ABSTRACT

A novel drill for the aerification of turf grasses is disclosed. The drill comprises a chuck and a fluted turf drill bit held by the chuck. The chuck includes a locking mechanism which permits the chuck to rotate freely about its longitudinal axis when loaded in compression (as when the drill is inserted into the ground) but which locks, preventing rotation, when the drill is loaded in tension (such as when the drill is withdrawn from the soil). The drill bit has a smooth upper section and a fluted lower section. The smooth section decreases the probability of entangling the turf in the drill bit with subsequent lifting of the turf when the drill is withdrawn. The tip of the drill bit is adapted to provide a torque to the drill bit during insertion into the ground. Thus, the bit spirals into the ground upon insertion, but locks upon removal, thereby permitting the flutes of the bit to cut a cylindrical hole in the ground while removing soil from the hole by retaining it in the space between the flutes. The drill of the present invention may be used in aerators previously limited to solid or hollow-core tines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/527,611 filed Mar. 11, 2005, which is a continuation of United StatesProvisional Patent Application Ser. No. 60/450,847 filed Feb. 28, 2003,to which priority is claimed under 35 U.S.C. §120 and which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to soil aerification (or “aeration”). Moreparticularly, it relates to a method and apparatus for the aerificationof turf grasses using a self-rotating turf drill.

2. Description of the Related Art

What is Aerification

Aerification is a mechanical process that creates more air space in thesoil and promotes deeper rooting, thus helping plants stay healthy. Inmost cases, this is achieved by removing cores (often called plugs) andthen filling the holes with topdressing. Topdressing is often a certaingrade of sand which may have other amendments added to allow the soil tomaintain air space, improve water penetration, and encourage healthyroot growth. The sand is brushed or poured into the holes which areusually healed within several days.

The condition of turf largely depends on the events occurring below thesurface. For grass to grow, deep healthy roots are needed, and rootsrequire oxygen. In good soil, they receive oxygen from tiny pockets ofair trapped between soil and sand particles. On a sports field, theeveryday traffic from players combined with the weight of heavy mowingequipment causes the soil to become compacted and the air pockets onwhich the roots depend for oxygen are lost. Aerification is a mechanicalprocess that creates more air space in the soil and promotes deeperrooting, water percolation and compaction relief.

The practice of aerating turf is becoming increasingly widespread. Thebenefits of aerification include:

Improved water infiltration and better drainage

Deeper penetration of fertilizers

Improved plant rooting

Thatch control

Increased stress tolerance

Break up of sod layers that can restrict rooting and water movement

Release of toxic gases from soils

Increased drying and drainage of persistently wet soils

Loosening of soil, allowing for increased air space

Softening of sports fields to reduce risk of injury

In addition, putting green aerification can provide for additionalsurface smoothing.

Compaction Relief

Definition of Compaction

Compaction of sports playing fields and golf course tees, greens andfairways is an inevitable product of their use—golf carts, maintenancemachinery and feet all contribute to the process that is defined as “theconsolidation of soil particles.”

Compaction decreases water and oxygen movement in the soil, hinders rootgrowth and lessens the ability of the soil to drain. Soil compactioncauses these negative effects by turning macropores (larger voids in thesoil largely responsible for drainage and air flow) into many micropores(smaller voids that hold water). As compaction increases, bulk densityalso usually increases, which means that more soil solids occupy a unitvolume of soil, reducing the porosity.

With turfgrass, techniques used to relieve compaction must be effectivewithout being highly visible. Aerification—either with solid tines thatcreate a hole in the soil, or with hollow tines or drills that remove acore of soil—is one of the more common ways of improving compactedsoils.

When a soil compaction condition is accompanied by excessive thatchbuildup, as is almost always the case in poorly maintained turf, eachcondition contributes to the effect of the other. Thatch is a mat ofundecomposed plant material (e.g., grass clippings) accumulated next tothe soil in a grassy area (as a lawn, sports field or putting green). Itis a tightly intermingled layer of living and dead stems, leaves androots of grasses, which develops between the layer of green vegetationand the soil surface. When thatch exceeds about ½ inch of undecomposedmaterial, it acts as a barrier to water and air infiltration into thesoil below and will provide an environment encouraging turf diseases andharmful insects. Compacted soils, on the other hand, are subject togreater temperature extremes than loose soils, because of limited airmovement; microbial activity necessary to thatch decomposition isreduced or halted.

Water that cannot penetrate the soil runs off or accumulates in lowspots where it harbors fungus growth.

Alleviating either condition will help, but only when thatch is keptunder control and the soil is properly aerified will turf have the bestchance for healthy, vigorous growth and disease resistance.

The accumulation of organic matter (thatch) and fine particles (siltand/or clay) can, over time, produce a surface layer that reducesporosity. Aerification can modify the profile, improving oxygen, water,and root movement, especially when the use of hollow tines or turfdrills is combined with core removal and backfilling channels withhigh-quality topdressing sand.

Prior Art Methods of Aerification

Turfgrass cultivation activities include hollow tine aerification, solidtine aerification, spiking, slicing, and water injection. Theseactivities, to varying degrees, can reduce thatch, prepare turf foroverseeding, and relieve soil compaction. Perhaps the best machine forworking large areas is a piston driven aerator that thrusts the corecutters vertically. Direct up and down coring leaves a clearly definedhole. Drum-type roller aerators will work but may cause tearing damageto the remaining grass since this type of cutter enters the turf at oneangle, moves in an arc with the drum movement, and is withdrawn at adifferent angle.

Solid Tine

Solid-tine aerification allows turf managers to aerate more frequently,since the procedure produces less surface disruption. Solid tines largerthan ¼ inch in diameter open turf to allow water and air infiltration,but the process compresses displaced soil downward and to the sides.This actually increases soil compaction around newly createdaerification holes. Repeated solid-tine aerification withlarger-diameter tines can create a hardpan at the aerating depth.

Related to solid tine aerification are slicing and spiking aerifiers.Slicing, spiking, and solid tine aerification do not pull plugs of soilfrom the turf. Slicing aerifiers cut thin slits into the soil andspiking aerifiers cut thin, triangular-shaped holes in turf. While theydo not relieve soil compaction as efficiently as hollow tineaerification, these practices cause less surface disruption and can bedone anytime.

Hollow Tine

These devices pull out plugs of soil that are deposited on the surface.One of the most common operations that one can perform using a hollowtine aerator is conducting a soil exchange program, offering theprofessional an ideal opportunity to remove soil cores and replace themwith a suitable top dressing, altering the soil profile.

Self-powered hollow tine aerifiers (core aerifiers) insert hollow tinesinto the soil, removing a soil plug ¼″ to ¾″ in diameter and 2″ to 12″deep, depending on soil type, soil moisture, and type of machine. Corespacing varies depending upon the make and model of the machine. Ingeneral, the more cores removed per square foot, the more effective thecultivation will be; removing fifteen to thirty cores per square foot isrecommended. Hollow tine aerification is considered the most efficientcompaction reliever of the prior art methods. It is preferably doneduring active turf growth.

Slitting

Using triangular blades ranging in size 100-250 mm (4″ to 10″), thesemachines create lots of short, narrow, close slits; slitting is usefulfor getting air down into the soil; it's quick; it does a fair job indethatching; however, this approach is not highly effective at reducingcompaction. Slitting also has its benefits, particularly in autumn whenit can be employed to help ‘connect’ the surface of the soil with theunderlying drainage layers. In the spring and summer, slitting ensuresthat water from rain and irrigation soak through the turf rather thanbeing shed in a sideways fashion by the thatch.

Water Injection

Water injection aerification is a recently-introduced method of turfaerification. Water, under high pressure, is injected into the turfsurface to relieve soil compaction. In addition, it can be used toinject turf management chemicals into the soil. It causes little surfacedisruption and can be done anytime during the growing season. This newtechnology has not been commonly available for use outside of golfcourse applications.

Deep Drill Aerification

Drill-type aerifiers employ rotating turf drills. The drill bitseliminate compaction along the sides and bottom of the aerificationhole, and allow for quick and effective penetration even in heavilycompacted soils including hardpan, muck and roots. The “gentlefootprint” of drill-type aerifiers, in conjunction with the absence ofcyclic vibration and the “straight in, straight out” action of the drillbits, gives this type of machine the capability of aerating fields thatare wet, dry or experiencing periods of high stress.

Deep drill aerifiers are also preferred for use in all problem areasbecause the rotating drill bits will penetrate subsoil areas, whereother machines tend to walk or bounce, often causing trauma to theplaying surface. Turf drill bits fracture the cylinder wall withoutglazing, thereby allowing lateral movement of air and water. “Drill &Fill” aerifiers are available which back-fill the drilled holes with aselected top dressing, usually sand, thereby modifying the soil profile.

Turf drill bits are commercially available in ⅝″×12″, ⅝″×16″, ¾″×12″,and 1″×12″ sizes. One particular deep drill aerifier currently on themarket produces 5″ spacing of holes. Drill aerification is especiallypreferred when one must penetrate hard soils. However, drillaerification is a very slow process as compared to reciprocating typeaerifiers.

As noted above, aerification has the added benefit of smoothing thesurface of a putting green. The process of punching holes and eitherreincorporating the plugs brought up or removing the plugs and fillingthe channels can offer some surface smoothing. Surface topdressing alonewill fill/smooth low spots. The combination of aerifying and thefollow-up topdressing will, over time, both fill low spots and softenhigh spots, resulting in more efficient surface smoothing thantopdressing alone.

SUMMARY OF THE INVENTION

The method and apparatus of the present invention combines the speed andmechanical simplicity of solid or hollow tine aerification with thepenetration depth, clean cutting and cylinder wall fracturing of deepdrill aerification. A turf drill is held in a chuck which permits freerotation of the drill bit when it is pushed into the ground (loaded incompression) but which restricts rotation of the bit when it iswithdrawn from the ground (loaded in tension). When the chuck is lockedand the drill bit is pulled from the soil, the flutes on the bit cut aclean, generally cylindrical hole in the soil with minimal compaction ofthe surrounding earth. In one embodiment, the drill bit comprises anon-fluted upper portion which helps prevent entanglement and lifting ofthe turf as the bit is withdrawn.

In some embodiments, the distal end of the drill bit is provided withopposing beveled surfaces which impart a rotational movement to the bitas it is pushed into the soil. Since the bit is self-rotating, there isno need for rotational means in the aerifier head, and therefore drillsaccording to the present invention can be utilized in aerifierspreviously equipped with solid or hollow-core tines. Since rotationalmeans are not needed in the aerifier's heads, the tines may be placed ingreater proximity to one another which permits greater density ofaerification holes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cut-away view of a simplified, reciprocating-typeaerifier equipped with a turf drill according to the present invention.

FIG. 2 is a partial cross-sectional view of the chuck of the presentinvention in its free rotation state.

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2.

FIG. 4 is a side view of the lower portion of the central shaft of thechuck.

FIG. 5 is a partial cross-sectional view of the chuck of the presentinvention in its locked, rotation-inhibiting state.

FIG. 6 is a side view of a drill bit according to the present invention.

FIG. 7 is an end view of the tip of the drill bit illustrated in FIG. 6taken along line 7-7.

FIG. 8 is an enlarged, side view of the tip of the drill bit illustratedin FIG. 6.

FIG. 9 is an enlarged, side view of the tip of the drill bit illustratedin FIG. 6 rotated 90°.

FIG. 10 is a partial cross-sectional view of another embodiment of thechuck of the present invention in its free rotation state.

FIG. 11 is a cross-sectional view taken along line 11-11 in FIG. 10.

FIG. 12 is a cross section taken along line 12-12 in FIG. 10.

FIG. 13 is a partial cross-sectional view an alternative embodiment ofthe chuck of the present invention in its locked, rotation-inhibitingstate.

DETAILED DESCRIPTION

In the following description, “drill” should be understood to mean anapparatus comprising both a drill chuck and a drill bit held within thechuck.

Referring now to FIG. 1, a portion of a reciprocating turf aerator isshown as a partial cut-away drawing. The aerator is shown in simplifiedform to illustrate how the turf drill of the present invention may beused in practice. Aerator 12 may be moved across an expanse of groundsuch as soil 22 on wheel(s) 14. Reciprocating heads 20 are connected tocrankshaft 16 by connecting rods 18 which cause heads 20 to movegenerally up and down as crankshaft 16 rotates. Drills 10, attached toheads 20, are thereby alternately thrust into and withdrawn from soil22. In some commercially-available aerators, crankshaft 16 is driven bythe power take off (PTO) of a tractor used to pull aerator 12 across aputting green, for example.

As mentioned above, this is a simplified view of a reciprocatingaerator. Commercial aerators are typically equipped with articulatingheads that additionally move fore and aft relative to the track of theaerator across the ground such that during insertion, withdrawal and theinterval there between during which the drill bits are in the soil, theheads and drills (or tines) do not move transversely with respect to theground. In this way, cylindrical, vertical holes may be achieved whilethe aerator advances continuously across the ground. Apparatus whichprovide this type of motion are described in U.S. Pat. No. 6,041,869entitled “Turf Aerator with Constantly Vertical Tines” and are availablefrom manufacturers such as Redexim/Charterhouse, Jacobsen (under theRyan brand name) and others.

The chuck 24 of one particular embodiment of the present invention isshown in partial cross section in FIG. 2. Shaft 26 may be adapted at itsupper or distal end to engage the head platforms 20 of a mechanicalaerator. Reciprocating aerators are particularly preferred, but thedrill embodiments illustrated in the drawing figures can be employed ina variety of aerators.

The proximal end (lower end in FIG. 2) of shaft 26 is contained withinrotating body 28 of chuck 24 and is rotatably supported by bushing 30and thrust bearing 32. In the particular embodiment illustrated in FIG.2, the proximal end of shaft 26 has conical tip 48 (see FIG. 4) whichfits within a corresponding conical portion of bearing 32. Bushing 30and thrust bearing 32 may be fabricated from a softer metal than thatused for shaft 26 to reduce frictional wear. Additionally, chuck 24 maybe provided with grease fitting 36 (also known as a Zerk fitting)through which a suitable lubricant may be introduced for lubricatingshaft 26 within bushing 30 and bearing 32. One preferred lubricant islithium grease. In other embodiments of chuck 24, self-lubricatingbearings and bushings may be used, in which case it may not be necessaryto provide means for introducing lubricant from an external supply.

Shaft 26 is free to both rotate within bushing 30 and thrust bearing 32and to slide longitudinally (within limits, as described below) withinbushing 30 and the upper, cylindrical portion of thrust bearing 32. Asindicated by the arrow in FIG. 2, chuck 24 is shown loaded incompression such as would occur when the drill was being pushed into theground. The conical tip at the proximal end of shaft 26 is shown fullyengaged in thrust bearing 32 in FIG. 2 as it would be during insertionof the drill in the ground.

Chuck 24 comprises a lock which engages when a turf bit held in thechuck is loaded in tension and which disengages when the bit is loadedin compression. In the embodiment illustrated in FIG. 2, rotating body28 has an opposing pair of set screws 34. The set screws 34 have aconventional threaded portion for engaging the threads of tapped holeswithin rotating body 28 and also a cylindrical tip 35 of reduceddiameter which is sized to project into the upper central bore ofrotating body 28. Such set screws are sometimes referred to as “dogpoint” set screws. In the embodiment illustrated, the holes in rotatingbody 28 into which set screws 34 are screwed are not threaded the fullthickness of the wall of rotating body 28. Rather, the threads begin atthe exterior surface of rotating body 28 and end prior to reaching thecentral bore of rotating body 28. In this way, the insertion ofprojecting points 35 may be limited. It is preferred that projectingpoints 35 do not contact shaft 26 when set screws 34 are fully seatedwithin rotating body 28. The rotation and sliding of shaft 26 withinrotating body 28 would be inhibited if projecting tips 35 were tocontact shaft 26. Alternatively, bushing 30 may be sized and positionedsuch that the shoulders of set screws 34 contact bushing 30. In thisway, over-insertion of set screws 34 may be prevented and bushing 30 maybe secured within rotating body 28.

As illustrated in the detail of FIG. 4, shaft 26 includes stop collar 44which prevents withdrawal of shaft 26 from rotating body 28 when atensile force is applied to shaft 26 (such as occurs during withdrawalof the drill from the soil). Stop collar 44 may be provided on its uppersurface with one or more indentions. In the embodiment illustrated, foursuch indentions are provided spaced 90° apart and each describes an arcof a circle in cross section. Indentations 46 and conical tips 35 of setscrews 34 are preferably sized such that projections 35 will seat inindentations 46 when stop collar 44 is brought into contact with setscrews 34. This condition is illustrated in FIG. 5.

FIG. 5 shows the same embodiment as that illustrated in FIG. 2. In thiscase, however, the drill is loaded in tension, as indicated by the arrowin the drawing. This condition obtains when the drill is being withdrawnfrom the soil and frictional forces on the drill bit 50 are opposing theupward motion imparted by the aerator. It will be noted that the conicaltip of shaft 26 is partly withdrawn from the conical portion of thrustbearing 32 and stop collar 44 is in contact with cylindrical projections35 of set screws 34. Further upward motion of shaft 26 relative torotating body 28 is thereby prevented. Since stop collar 44 may becoated with lubricant, contact of the upper surface of stop collar 44with cylindrical projections 35 may not inhibit the rotation of shaft 26relative to rotating body 28 until an opposing pair of indentations 46align with set screw projections 35 at which point shaft 26 may moveslightly further upward, seating projections 35 within indentations 46at which point further rotation of shaft 26 is significantly inhibited.It will be appreciated that the number and spacing of set screws 34 inrotating body 28 and the number and spacing of indentations 46 in stopcollar 44 may vary from that of the embodiment shown in FIGS. 2 through5.

Also shown in FIGS. 2 and 5 is dirt shield 38 which may be used to helpdeflect dirt, sand and other soil components from the interface ofbushing 30 and shaft 26. Dirt shield 38 may be a stamped metal fittingwhich is concentric with shaft 26. Rotating body 28 may also be providedwith chamfer 42 to further aid in the shedding of dirt from the top ofrotating body 28. In operation in aerifiers having multiple drills inclose proximity one to another, dirt particles are often thrown up bythe drills as they are withdrawn from the ground which particles mayland on nearby drill chucks. It is, of course, advantageous to shieldbearings from the introduction of abrasive particles.

Also shown in FIG. 2 and FIG. 5 is the upper portion of the shank ofturf drill bit 50. Rotating body 28 is provided with a central bore onits lower surface for receiving drill bit 50. Drill bit 50 may beprovided with notch or flat 52 for engaging set screw 40 which bothretains bit 50 within chuck 24 and prevents the rotation of bit 50relative to rotating body 28. In the illustrated embodiment, set screw40 is shown as being a dog point set screw. Set screw 40 may be aconventional set screw, but it may be convenient to have set screw 40 beof the same type and size as set screws 34 so as to reduce inventory andreplacement parts requirements and to reduce the chance that aconventional set screw would be inserted in place of set screw 34thereby impairing the function of chuck 24. Alternatively, set screw 40may be a different diameter from that of set screws 34.

As will be appreciated by those skilled in the art, there are many waysa drill bit may be secured in a chuck. The securing method using a setscrew described above and illustrated in the drawing figures has beenfound to be particularly suited to the application of the invention, butother methods may be used. By way of example, a hole may be provided inthe chuck with a corresponding hole in the bit shank. A pin (such as aroll pin) or a machine screw passing through the hole in the chuck andinto the hole in the bit shank would secure the bit in the chuck.

One embodiment of a drill bit of the present invention is shown in FIG.6. Bit or drill tine 50 is comprised of an unfluted, generallycylindrical upper portion 54 and a lower, fluted section 56. As notedabove, the upper portion of the shank of bit 50 may be provided withflat or notch 52 which provides a planar contact area for set screw 40of chuck 24 used to secure bit 50 in the lower central bore of rotatingbody 28.

Flutes 58, which may be generally rectangular in cross-section, areformed in a helical pattern around core or central shaft 62. Smoothportion 54 is provided to lessen the chance of turf entanglement whenthe bit is withdrawn from the turf. In practice, the insertion depth maybe adjusted such that fluted portion 56 penetrates to a soil depth justbelow the turf layer while portion 54 is within the turf layer.

Details of the tip of bit 50 are shown in FIGS. 7, 8 and 9. The tip maybe formed by grinding generally planar, opposing flats 60 at the angleshown as α in FIG. 8. The position of notch 52 is shown as a dashed linein FIG. 7 to illustrate the angular position of the dividing line or“chisel edge” between the opposing flats 60. It will be noted that flats60 are offset from each other with respect to the center line of thebit. Because of this offset, a torque is imparted to bit 50(counterclockwise as viewed in FIG. 7) when it is inserted into theground. Thus, when bit 50 is pushed into the ground by an aerator, ittends to rotate about its longitudinal axis and the flutes 58 create apair of helical grooves in the soil around the central hole created bythe displacement of the soil by central shaft 62.

Conventional turf drills typically are carbide tipped to maintainsharpness for an adequate length of time. It has been surprisingly foundthat the drill bits of the present invention do not require carbide tipsor inserts to provide adequate service life. The drill bits of thepresent invention rotate about 2½ revolutions per insertion. Incontrast, bits used in conventional turf drilling machines rotate about25 revolutions per insertion. It is contemplated that the reduction infriction engendered by the factor of 10 decrease in rotations perinsertion is responsible for the longer-wearing nature of the bits ofthe present invention.

In one particularly preferred embodiment, L₁ is about 10½ inches, L₂ isabout 7½ inches and D, the drill tine's diameter, is about ½ inch. Theshank diameter may be chosen to fit the head of the particular aeratorto be used and it may be greater than, less than, or the same as thetine diameter. In this embodiment, the diameter of central shaft or core62 is about ¼ inch and the flutes 58 are about 0.1 inch wide (thick) and0.125 inch high. The twist length, the linear distance over which aflute makes a complete revolution about central shaft 62, is about 3inches. The tip angle (αin FIG. 8) is about 45°. A particularlypreferred drill tine is fabricated from American Iron and SteelInstitute (AISI) Grade 4140 steel heat treated after fabrication to avalue of at least about 50 on the Rockwell “C Scale” of hardness.Following heat treatment, drill tine 50 may be shot-peen finished.

It will be appreciated by those skilled in the art that there are manymeans for effecting the locking feature of the chuck of the presentinvention. By way of example, one such alternative is shown in FIGS. 10through 13, inclusive. In this embodiment, a spline 70 or splines 70 onshaft 26 is used in conjunction with keyway 69 or keyways 69 in lockingmember 68 held within rotating body 28.

In the embodiment illustrated, bushing 30 is held within upper bore 72of rotating body 28 by retaining ring 64 which fits within groove 65 inthe wall of upper bore 72. Locking member 68 which may include aplurality of keyways 69 rests on shoulder 73 at the lower boundary ofupper bore 72. Thrust washer 66 may be provided between locking member68 and bushing 30 to protect the relatively softer material of bushing30 from impact with splines 70 of shaft 26 when shaft 26 slides upward.Keyways 69 are sized and spaced such that splines 70 will fit withinthem when shaft 26 is urged upward (loaded in tension) and rotating body28 rotates relative to shaft 26 until the splines 70 and keyways 69align. FIG. 10 shows chuck 24 loaded in compression (as during insertionof the drill into the ground). In this condition, splines 70 are belowlocking member 68 and thus rotating body 28 can freely rotate relativeto shaft 26. FIG. 13 shows chuck 24 loaded in tension (as occurs duringwithdrawal of the drill from the ground). In this condition, splines 70engage keyways 69 in locking member 68 and rotation of rotating body 28(and bit 50) relative to shaft 26 is prevented.

Locking member 68 may be fabricated as an extrusion cross cut to thedesired thickness. Rotating body 28 may be heated to expand the diameterof upper bore 72 and locking member 68 inserted while the bore isexpanded. Upon cooling and contraction, locking member 68 (ifappropriately sized) will be rotatably secured within upper bore 72.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

1. A turf drill chuck comprising: a receiver for holding a turf drillbit; a stud for mounting the chuck in a chuck holder; an arbor whichmoves longitudinally between a first position when a compressive forceis applied to the arbor and a second position when a tensile force isapplied to the arbor; and, a lock which engages when the arbor is in thesecond position and which prevents rotation of the arbor.
 2. A turfdrill chuck as recited in claim 1 wherein the lock comprises a splineand a keyway.
 3. A turf drill chuck as recited in claim 1 wherein thelock comprises a generally cylindrical member which engages a memberhaving a depression sized to fit the cylindrical member.
 4. A chuck fora turf drill comprising: a rotating body having an upper central boreand a lower central bore for receiving the shank of a turf drill, theupper central bore having an upper cylindrical bushing and a lowerbushing having a generally conical recess and the lower central borehaving a set screw for engaging the shank of a turf drill inserted inthe lower central bore; at least one set screw in the side of therotating body having a generally cylindrical projection on one endthereof which projects into the upper central bore of the rotating bodywhen the set screw is fully engaged in the side of the rotating body,and, a generally cylindrical shaft having a first end adapted to connectto a turf aerator and an opposing second end sized to rotatably andslidably fit within the upper central bore of the rotating body, saidsecond end having a generally conical end adapted to fit within theconical recess of the lower bushing of the rotating body and a stopcollar for preventing the withdrawal of the shaft from the upper centralbore of the rotating body when a tensile force is applied to the shaft,the stop collar having an upper surface and a lower surface, said uppersurface having at least one lateral depression sized and shaped toengage the generally cylindrical projection of the set screw in the sideof the rotating body when a tensile force is applied to the shaft andtorque is applied to the rotating body sufficient to rotate the rotatingbody such that the set screw projection is in axial alignment with thelateral depression in the upper surface of the stop collar therebypreventing further rotation of the rotating body around the shaft in theupper central bore of the rotating body.
 5. A turf drill chuckcomprising: a generally cylindrical body having a first end and a secondend; means for engaging a turf drill bit at the first end of the body;means within the body for allowing rotation of an engaged drill bitresponsive to insertion of the drill bit into turf; and, means withinthe body for preventing rotation of the drill bit responsive towithdrawal from the turf.
 6. A turf drill chuck comprising: means forengaging a turf drill bit; and, means for allowing rotation of anengaged drill bit in response to a compressive force applied to thedrill bit and preventing rotation of the drill bit in response to atensile force applied to the drill bit.
 7. A chuck for a turf drill asrecited in claim 4 wherein the upper bushing and the lower bushing areself-lubricating.
 8. A chuck for a turf drill as recited in claim 4further comprising a grease fitting on the rotating body in fluidcommunication with the upper central bore of the rotating body forlubricating the shaft engaged by the upper and lower bushings of therotating body.